Which viral infection poses an increased risk for aplastic crisis in patients with hemolytic anemia?

Parvovirus B19 is known for its association with aplastic crisis, particularly in patients with underlying hemolytic anemia. This virus specifically infects and destroys erythroid progenitor cells in the bone marrow, which are responsible for red blood cell production. In individuals with hemolytic anemia—such as those with sickle cell disease or hereditary spherocytosis—their red blood cell production is already compromised. When they encounter Parvovirus B19, the additional suppression of erythropoiesis can lead to a rapid decline in hemoglobin levels and result in an aplastic crisis.

In the context of other viral infections mentioned, while cytomegalovirus (CMV), varicella-zoster virus (VZV), and Epstein-Barr virus (EBV) can cause various complications in immunocompromised patients or affect blood cells, they do not have the same direct destructive effect on erythroid progenitor cells as Parvovirus B19 does. Therefore, the unique interaction of Parvovirus B19 with the bone marrow makes it the infection with the greatest risk of triggering an aplastic crisis in patients already suffering from conditions that cause hemolytic anemia.